Step 1: step 1

Step 2: To make the filling, heat the olive oil in a pan until it starts to shimmer. Add the leek and sauté until soft but not coloured. Stir in the ham with a wooden spoon, fry for 1 min, then stir in the flour and fry over a medium heat, stirring occasionally, until the mixture is golden but not burnt – this will take about 5 mins.

Step 3: step 2

Step 4: Meanwhile, combine the stock and milk in a small pan and heat until steaming but not boiling. Season with a few scrapes of nutmeg. Gradually add the liquid, a few tbsp at a time, stirring constantly.

Step 5: step 3

Step 6: Once you’ve incorporated all the milk stock, continue to cook the filling over a medium heat for about 10 mins or until it thickens and leaves the sides of the pan when you stir it.

Step 7: step 4

Step 8: Season with black pepper, taste and adjust the salt if necessary – the ham can be very salty to start with. The filling is now done: it has to be really thick because you don’t want the croquetas to turn into pancakes.

Step 9: step 5

Step 10: Smooth the mixture onto a baking tray (30 x 20cm is fine). Once it has stopped steaming, cover with cling film to stop it drying out. Leave to cool before putting it in the fridge for 1 hr.

Step 11: step 6

Step 12: When you're ready for the next stage, line up three bowls: the first filled with the flour, the second with beaten egg and the third with breadcrumbs. Take the ham mixture out of the fridge. Put a little bit of olive oil on your hands to make it easier to roll the croquetas.

Step 13: step 7

Step 14: Roll a spoonful of the mixture between your palms. The size and shape of the croquetas is up to you, but the easiest is a walnut-sized ball. Then begin coating as follows.

Step 15: step 8

Step 16: Dunk the croquetas into the flour – you want a dusting – followed by the egg, then the breadcrumbs. Put them on a tray and, when you’ve used up all the mixture, place in the fridge for 30 mins.

Step 17: step 9

Step 18: If you have a deep-fat fryer, heat the oil to 180C and fry for a couple of mins. If not, heat the oil in a deep, heavy-bottomed saucepan until it starts to shimmer. Then add 5-6 croquetas at a time and fry until golden all over. Once cooked, drain on kitchen paper and eat straight away.